Method and apparatus for separating and drying comminuted solids



Feb. 23, 1954 N, L .'DAvls 2,670,078

METHOD AND APPARATUS FOR SEPARATING AND DRYING COMMINUTED SOLIDS FiledJan. 12, 1949 2 Sheets-Sheet l l Il lo Feb. 23, 1954 2,670,078

N. L. A DAVIS METHOD AND APPARATUS FOR SEPARATING AND DRYING COMMINUTEDSOLIDS Filed Jan. 12, 1949 2 Sheets-Sheet 2 Patented Feb. 23, 1954METHOD AND APPARATUS FOR SEPARAT- ING AND DRYING COMMI-NUTED S'OLIDSINelson L. Davis, Chicago, Ill.

Application January'l, 1949, Serial N c. 70,471

My invention relates to improvements in float and sink separation anddrying oi? solid materials and has for one object to provideanappara'tus and process which may be used for' the separation orcleaning and drying of. coal, ore and the like, by means of a highvolatile heavy liquid medium.

Another object of my invention is to provide afloat andvs'ink processvand apparatus wherein the'heavy medium liquid used in the float and sinkprocess is entirely contained within thevsystem and is recirculated inan enclosed apparatus and system without ycontamination by outside air.

Another object of rnyinvention is to provide a process and apparatuswherein moist or wet coal-or ore may be by one single continuous processand in one single apparatus separated according to `different specificgravities and dried or freed from water.

Other objects will appear from time to time throughout the -specicationand claims.

My invention is illustrated more or less diagrammatically in theaccompanying drawing, wherein:

Figure l is a vertical longitudinal section;

Figure i2 is a section along the line 2-2 of Figure l; and I 'Figure 3is a sectionalong the line '3 3 of Figure'l.

Like pa-rts are indicated by like characters'4 throughout thespecilication land drawing.

-The heavy medium thatI propose to use vis a high volatile chemicalliquid such as chlorinated hydrocarbon which has toxic or poisonouscharacteristics and it is essential therefore that the medium be sohandled that vit never escapes from the system 'and that both `the iioatand sink material, when vdischarged from the iioat and sinkvessel,becompletely'freed of the heavy medium.

'This medium is heavier than water. y It is immiscible with water -andwhenfsolids wet with Water 'are immersed in a bath `oi the heavy medium,the waterfloats to the top of theheavy medium bath and forms a layer of'water supernatant on'the heavy mediumbath. A Most if 'not all of thewater associated with the solidsfwill be-i'epla'ced by the heavy.medium'and 4forced upwardly through the heavy medium 4bath and asolidsretaining screen to join the supernatant water layer.

'it is'a'i'loat and' sink'vessel' having atfthebottom a. vscrew conveyori2 extending 4longitudinally thereof and above the ibottom but blow .thetop v7 claims. (o1. 209-172) screw conveyor 3 extending longitudinallythereof. 4 is a .cover for the vessel. 5 indicates, .as will hereinafterappear, the level of the heavy parting liquid. 6 isa screen extendingacross the vessel, furnishing a housing for the screw conveyors 3, whichconveyors closely fit the screen.

with liquid discharge vtroughs 8, the weirsand troughs being alsoenclosed A'by the coverll. 9 is an .annular refuse boot into which therefuse conveyor .2 discharges. Theiboot contains .an elevating bucketwheel, the buckets i0 of which are perforate. The boot B'communicatesabove the vvessel cover 4 with .a refuse conveyor .trough H 'in which isa refuse screw conveyor |72. i3 is a cover for the trough Il and thevoutboard end of the-trough Il discharges into achute M and 4thence intoa refuse belt conveyor i5. IB is an yannular boot communicating `withthe vessel l, there being an aperture between them so thatthe screwconveyors .3 `discharge into the boot I6. The boot lr6 contains anelevating bucket wheel having perforate buckets l1 yadapted todischargeintoftroughs i8 .containing screw conveyors |9,.the .trough It beingclosed .bye cover 20. The screw conveyors I9 discharge through fa chute2| onto a fbelt, conveyorV 22.r 23 is a feed trough extending laterallyfrom the feedend of 'the vessel l. Thescrew conveyors 3 extend'outwardly `from `the vessel intothefeed trough. The Vfeed ytrough is.closed vat .24 and communicates with a feed hopper ,25, which in turnreceives the feed ythrough a .chuteZ .227 serves .asa coverfor .thechute 2E. and hopper 25. 28 is a Weir box which receivesoveriiow 'fromthe troughs 58 `and :discharges 'through `thegpipe 29..

30 `indicates similar pipes vforming part of 1.a

steam heating system, the detailsof .which v,are not shown but whichcommunicate `with "steam jackets f3l, `32 Aabout the "troughs Il and i8iso.

'l indicates weir's formed by the upper edges of the vessel walls whichare associated i which contains the condenser coils and spent coolingwater is discharged through the pipe 54. Pipe 55 leads from the upperportion of the condenser to the trough il and the pipe 56 to the troughIB.

SEI is a pipe joining the feed hopper 25 and the vessel I above theheavy medium level.

It will be realized that whereas I have illustrated and described anoperative device, still many changes might be made in the size, shape,number and disposition of parts without departing materially from thespirit of my invention. I wish, therefore, that my showing be taken as1n a broad sense as diagrammatic and illustrative rather than limitingme to the precise showing.

The use and operation of my invention are as follows:

The vessel is rst filled with the heavy medmm to the level approximatelyas indicated at E. Under these circumstances the heavy medium will standat the same level in the vessel in the two conveyor boots 9 and IB andin the feed hopper 25. Water will then be added to cover the heavymedium with a continuous sheet of water. This water level will beequaliaed through the pipe SB in the vessel and in the feed hopper 25but since the level of the heavy medium was above the openings betweenthe vessel and the two boots, no water will enter them but the level ofthe heavy medium will rise in both boots a distance sufiicient tocompensate for the added pressure made by the water in the system.

The solids to be treated which for example might well be coal with mixedrefuse, slate bone, etc. and which normally have a substantial amount ofadhering water, will be introduced into the feed hopper. Some of thesolids will sink to the bottom of the hopper, other of the solids willtend to float. The screw conveyors will operate to propel the solidsfrom the feed hopper into the vessel. The continuing supply of solidsinto the feed hopper will insure the downward movement of both sink andfloat material to bring it into the range of operation of the screwconveyor. Some of the adhering water will be forced upwardly as thematerial is immersed in the heavy liquid and there will be a gradualincrease of the amount of water in the system as a result of thecontinuous introduction of water laden solids. As the solids are fedinto the vessel, the heavy material will sink to the bottom while thelighter material will flow up. Its upward movement will be limited bythe screen troughs which enclose the upper portions of the screwconveyors 3 and so the float material will be propelled across the tankbel-ow the level of the heavy medium and out of contact with the water.The sink material will be propelled in the opposite direction by theconveyor 2. The conveyors will agitate the heavy medium and the solidstherein contained suiciently to permit a continuous upward movement ofthe water through the heavy medium through the screen to join thesupernatant water layer. As the process continues, the vessel will filluntil the water is discharged over the weirs 'i from the system and suchwater will continue to be discharged at the same rate as it isintroduced with the solids.

The solids will continuously be discharged by the screw rconveyors 2 and3, the sink material going into the boot S, the float material into theboot I5. The bucket wheels will raise this material above the levelofthe heavy medium and altogether out of contact with the water. Becausethe buckets are perforate, f most of the heavy medium will drain off asthe bucket wheel elevates the material above the level of the heavymedium so that both the coal and the refuse when discharged into thetroughs ii or i8 as the case may be, will be generally free of heavymedium except for that relatively small amount adhering to the surfaceof the solids.

The solids with whatever heavy medium is left adhering to them will bepropelled through the troughs il and I8. The temperature of thesetroughs and the material contained therein is raised by the steamjackets 3l and 32 high enough to vaporize the heavy medium and so bothrefuse and coal is discharged from the troughs in a dry, liquid free,condition.

The drying zones defined by these heated troughs are illustrated asbeing separate but of course there is no reason why the screw conveyorscould not all of them, if desired, be closed in a single housing andforming a single drying zone.

The solids propelled through these drying zones is thus free from heavymedium. It it should happen that some of the water has not been entirelyremoved from the solids, if an occasional entrapment of water by solidsduring the passage of heavy medium should occur, such entrapment will bevery limited and the temperature in the drying or vaporizing zone willbe such as to tend to vaporize some if not all of such small amoun ofwater.

The vaporized heavy medium will of course be mixed with a certain amountof air and perhaps with a certain amount of water vapor and this vaporand air will be drawn up from the heating zone through the blower intothe condenser. There the heavy medium will be condensed and the heavymedium and perhaps some water will be returned to the vessel above thelevel of the heavy medium. If any water is so returned, it will remainin the supernatant water layer while the heavy medium sinks to itslevel, and thus do no harm.

In order that the blower may not by any chance draw against the vacuumin the heating zones, the air which is returned from the condenser asindicated by pipes and 55 returns freely to the vaporizing zones.

This process and apparatus is directed primarily toward the treatment offine coal and refuse. If any of the coal, that is any of the oatmaterial is small enough to pass upwardly through the screen, it will bemixed with the water as it rises above the level of the heavy medium andwill ultimately be discharged over the Weir with the water and may bewasted, or recovered by conventional methods.

Another problem, however, rises in connection with the lines which iioatand that is the danger that they might clog the screen. That danger isminimized by the fact that the screw conveyors immediately beneath thescreen set up a zone of agitation suflicient to prevent such clogging,thus if necessary, other means might be used for occasionally freeingthe screen or cleaning it.

I have shown screw conveyors and bucket wheel elevators. Other conveyingmeans and other elevating means might be used.

Under some circumstances it might be desirable to have partitions orguides or broken flights Xed in the space between the buckets and thepoint where they receive the discharge from the screw conveyors toinsure a sufcient movement or agitation of the heavy medium and thesolids supported therein. Under ordinary 7 .float and sink componentsfrom the vessel, at a point below the level of the parting liquid.

4. A mineral separating apparatus including a vessel adapted to containa bath of heavy parting liquid, means for maintaining a layer of waterat generally constant level iioating on the parting liquid, means forintroducing solids to be separated including both float material lighterthan the parting liquid and sink .material heavier than the partingliquid into the vessel at a point below the level of the parting liquid,means for preventing the rise of the float material to the level oftheparting liquid, means for propelling the float component across thevessel beneath and in engagement with the means for preventing the riseof the ioat material, means for separately propelling the sink componentalongr `the bottom of the vessel, means for separately withdrawing theiioat and sink components from the vessel, at a point below the level ofthe parting liquid.

5. A mineral separation apparatus including a vessel, a cover therefor,a feed hopper, two connections between the hopper and the vessel, oneabove the other, a bath of heavy parting liquid adapted to be containedwithin the vessel and hopper, the level of the parting liquid beingbetween the two connections between the bath and hopper, means formaintaining a liquid sealwith in the hopper and the vessel comprising asupernatant layer of water on the bath the level ci which is above thelevel of the upper connec tion, an elevator boot communicating with the`vessel 'below the level of the heavy liquid bath, a vaporizing chamber,means for heating it to 'vaporize the liquid, a closed passage leadingfrom the boot to the chamber, means for propelling material through theboot, the passage and the vaporizing chamber and for discharging driedmaterial from the system, a cover for vthe vaporn izing chamber, acondenser, means for drawing vapor from the chamber to and through thecon denser to condense it, means for discharging condensed vapor inliquid form to the bath.

6. A mineral separation apparatus including a vessel, a cover therefor,a feed hopper, two conu hopper, means for maintaining a liquid sealwithin the hopper and the vessel comprising a supernatant layer of wateron the bath the level oi' which is above the level of the upperconnection, an elevator boot communicating with the vessel below thelevel of the heavy liquid bath, a vaporicing chamber, means for heatingit to vaporize the liquid, a closed passage leading from the boot tothe` chamber, means for propelling material through the boot, thepassage and the vaporizing chamber and for discharging dried materialfrom the system, a cover for the vaporizing chamber, a condenser, meansfor drawing vapor from the chamber to and through the condenser tocondense it, means for discharging condensed vapor in liquid form to thebath, means for returning gas and air from the condenser to thevaporizing zone, .means for withdrawing vapor from the feeding hopperand from the solids discharge to the condenser.

'1. The method of separating and removing water from mixed sink andfloat solids, which consists in immersing them in a bath of liquidheavier than, immiscible with, and more readily vaporized than water,the specific gravity of which is greater than that of some and less thanthat of 'other of the solids, permitting the sink material to descend tothe bottom of the bath while positively holding the float solids belowthe level of the heavy liquid, conveying the solids through the bathbelow the level of the heavy liquid in a continuous moving layer,agitating that layer of material to promote sink and float separationand to promote` adherent water to pass upwardly through the bath,withdrawing the solids from the bath and separately withdrawingsupernatant water from the surface of the bath.

NELSON L. DAVIS.

gesamtes cited in the fue of this patent UNITED STATES PATENTS

